iPhone 4 at least has support for Braille displays like those Brailliant, as kindly demonstrated by acoustic guitar virtuoso and software guru Victor Tasaran. Using the six buttons on his Brailliant-32 he's able to navigate across icons, then feel the text beneath each one -- or wait for the phone's hurried text-to-speech to read back to him. It's an encouraging solution for smartphone accessibility, but does have a rather negative impact on portability -- and, we're sad to say, on cost as well. His 32-character unit will set you back just under $4k, which is many times the cost of the phone itself. But, at least when it's used like in the video below, sitting on the table, he won't have to worry about signal issues.
Update: To be clear the text-to-speech is entirely being generated by the phone; it's a stock feature of iOS 4. The Brailliant is enabling Victor to cycle through icons, make selections, and "read" the on-screen text with his fingers.